Interactive, Image-Guided Surgery (IIGS) is a technique in which the three-dimensional position of any surgical instrument is tracked and that position is displayed on preoperatively obtained tomograms. The research proposed in this project is to extend beyond the initial application of IIGS, intracranial neurosurgery, and to expand the image information provided to the surgeon. The extension of this process will be to spinal surgeries. In order to apply IIGS techniques to spinal applications new forms of registration and display will have to be developed. Inherent in this process will be the development of automatic and semi-automatic segmentation techniques for structures in and about the spine. Intracranial IIGS has led to reduced damage to healthy tissue, smaller incisions, more complete resections and reduced time of surgery. Given the huge number of spinal surgeries relative to intracranial surgeries, if IIGS can provide the same advantages to spinal surgery as it does to intracranial surgeries, the rewards to health care would be enormous. The proposed expansion of the image information includes both vascular and realtime imaging formats. The vascular images will include both conventional projection angiograms and tomographic vascular images such as MRA and CTA. By using realtime imaging techniques such as endoscopy and B- Mode ultrasound in conjunction with tomographic image sets, the advantages of each may be preserved and the drawbacks to each mitigated.